The present invention relates to an electrophotographic image forming apparatus for forming an image on a transfer material of a copier or printer.
Many methods and apparatuses for obtaining color images using the electrophotographic method have been proposed. For example, as indicated in Japanese Patent Publication Open to Public Inspection No. 100770/1986, there is a method that latent images are formed on a photosensitive drum, which is an image forming unit, depending on the number of separated colors of an original image, they are transferred onto a transfer drum after being developed so as to form a multi-color image on the transfer drum, and they are then transferred onto a transfer material so as to obtain a color copy. An apparatus using this method requires a transfer drum which is large enough to transfer one sheet of image onto the peripheral surface thereof in addition to the photosensitive drum, and is inevitably large in size and complicated in structure.
Furthermore, for example, as indicated in Japanese Patent Publication Open to Public Inspection No. 149972/1986, there is a method that latent images are formed and developed on a photosensitive drum, depending on the number of separated colors of an original image and they are transferred onto a transfer material when they are developed so as to obtain a multi-color copy. It is difficult in this method to registrate many color images with high accuracy, and good quality color copies cannot be obtained.
Furthermore, there is a method that latent images are formed on a photosensitive drum depending on the number of separated colors of an original image and developed by color toners repeatedly and color toner images are registrated on the photosensitive drum and transferred so as to form a color image. This basic process of multi-color image forming is indicated in Japanese Patent Publication Open to Public Inspection Nos. 75850/1985, 6766/1985, 95456/1985, 95458/1985, and 158475/1985 by the applicant of this patent and others.
In a multi-color image forming apparatus for forming color images by registration like this, a plurality of developing units containing different color toners are installed around the photosensitive drum, and latent images on the photosensitive drum are developed generally by rotating the photosensitive drum several times so as to form color images.
In an image forming apparatus such as a monochromatic color analog copier using the electrophotographic method or a copier or printer using a semiconductor laser LED scanning system, an apparatus has been proposed in which a part of the image forming means is provided as a cartridge unit, for replenishing or replacing various photoconductors of limited durability, developer carriers, cleaning materials, and developer toners when they are exhausted, and the integrated unit of the essential units of these image forming means is removed for maintenance or replacement. Various configurations such that the feed path of a transfer material whereon an image is formed by the image forming means is opened so that the transfer material can be easily removed for clearing a jam have been proposed.
A typical configuration that a photosensitive drum, developing unit, and cleaner are integratedly mounted to a support member so that they can be removed from the main unit and each unit can be easily replaced or repaired is indicated in Japanese Patent Examined Publication No. 54392/1983. A configuration that the essential units of the image forming means are integrated and not reused is indicated in Japanese Patent Publication Open to Public Inspection No. 154255/1982, and a printer configuration that a non-reusable cartridge is used and latent images are formed on a photosensitive drum by dot exposure scanning by a semiconductor laser is indicated in Japanese Patent Publication Open to Public Inspection No. 147366/1984.
Furthermore, the above publications indicate a configuration that the upper frame of the division structure is opened so as to open the transfer material feed path, and the transfer material can be easily removed in case of jamming. Japanese Patent Publication Open to Public Inspection No. 154255/1982 mentioned above indicates a configuration that a non-reusable process cartridge is mounted to the upper frame of the bisecting structure so that it can be replaced, increasing operability of cartridge replacement and the ease of jam clearing. A configuration that priority is given to the ease of process cartridge replacement, such as a replenishment toner cartridge or a collection toner cleaning cartridge, and particularly a process cartridge, is mounted to the lower frame so as to improve the operability of maintenance, is indicated in Japanese Patent Publication Open to Public Inspection No. 1161/1983.
A configuration that a vertical type of the above structure is used so as to improve the same direction operation and jam clearing is indicated in Japanese Patent Publication Open to Public Inspection Nos. 244058/1988, 244059/1988, 244064/1988, and 179168/1989.
However, a compact printer having a process cartridge, which comprises a developing unit and an image carrying member, which can be easily mounted to or removed from the apparatus body, is free of leakage or spilling of toner or developer from the developing unit when it is mounted to or removed from the apparatus body, and free of such problems during clearing of a jammed transfer material, has not been proposed.
A proposal that when the upper frame of a printer of the bisecting structure is open, a process cartridge mounted to the upper frame is always kept horizontal so as to prevent waste toner from spilling is indicated in Japanese Patent publication Open to Public Inspection No. 90961/1983. Although this configuration allows the cartridge to be easily mounted or a jam to be easily cleared, problems such as spilling or leakage of toner when the cartridge is mounted, a jam is cleared, or a replacement operation is performed for maintenance are, has not been solved.
In Japanese Patent Publication Open to Public Inspection No. 72159/1983 that in a printer of the bisecting structure wherein a jam can be easily cleared, a non-reusable cartridge is mounted to the upper frame. In Japanese Patent Publication Open to Public Inspection No. 1161/1983, a replenishment or collection toner can be easily replaced, a process cartridge is mounted on the lower frame, and the process cartridge of a developing unit, cleaning unit, and photosensitive drum is held up for clearing a jam, the operability of process cartridge replacement conflicts with the ease of jam clearing. Furthermore, in these process cartridges, since the developing unit and the cleaning unit are mounted at the bottom across the paper feed path from the transfer pole, toner spills from the developing unit or the cleaning unit even if the process cartridge is surely sealed when the process cartridge is replaced or external vibration or shock is applied to the apparatus body, causing the inside of the apparatus or the transfer paper to become soiled.
The printer indicated in Japanese Patent Publication Open to Public Inspection No. 195357/1988 contains a process cartridge and forms a flat paper feed path at the upper part. However, there are some restrictions on the feed path from the transfer material separation unit of the photosensitive drum to the fixing unit, and problems of the feed unit have not been solved. Furthermore, the printer lacks ease of jam clearing when open, and compactness as a whole due to the upstanding stack paper feed configuration, and the opening angle of the upper frame is restricted. Therefore, the printer is not an apparatus which is superior in operability.
As to a color image forming unit, as described previously, a belt type image forming unit wherein a photoconductor is coated or deposited on a flexible belt has been proposed, for example, in Japanese Patent Application No. 192874/1989 by the applicant of this patent together with a photosensitive drum wherein a photoconductor is coated or deposited on the peripheral surface of the drum. The belt type image forming unit (hereinafter called a photosensitive belt) is determined in shape by stretching between rotating rollers including a drive roller, and is effective in configuring a compact color image forming apparatus using space effectively. Since the photosensitive belt can move along a small curvature, defective separation of a transfer material can be prevented by separating the transfer material using the curvature of a rotating roller with a small diameter.
In a color image forming apparatus using such a photosensitive belt, image forming means such as a charging means, an image exposure means, a plurality of developing units, and a cleaning means are installed mainly below the lower surface of the outer peripheral surface of the photosensitive belt, and those image forming means are integrated in a process cartridge together with the photosensitive belt, and the process cartridge can be freely mounted to or removed from the apparatus body.
A transfer material whereon a color toner image is transferred is ejected onto a paper ejection tray installed on the top of the apparatus with the copy side down. Therefore, the necessary area of a place where the apparatus is to be installed is small.
A configuration that problems of paper feed and jam clearing are solved by using a compact cartridge and same side operation is possible is indicated in Japanese Patent Publication Open to Public Inspection Nos. 40850/1989 and 244059/1988.
A control for outputting an indication when toner of a process cartridge is exhausted or the photoconductor life expires is indicated in Japanese Patent Publication Open to Public Inspection No. 85763/1988. However, an image forming apparatus, which is compact and easy to operate and satisfies all the requirements such as easy jam clearing, no spilling of toner during operation of the cartridge, easy cartridge replacement, and all operations available from one side via the front of the apparatus body, has not been proposed.
Furthermore, the present invention relates to an image forming apparatus for forming a toner image on an image carrying member by the electrophotographic method and transferring the toner image onto a transfer material so as to obtain an image, particularly in an image forming apparatus such as a printer, copier, or facsimile equipment wherein a process cartridge comprising an image carrying member integrated with at least one of a developing means and cleaning means can be freely mounted or removed.
Image forming apparatuses have come into wide use recently according to the needs of the times such as sophisticated information oriented society and individuals. Since there were not so many image forming apparatuses installed earlier, maintenance and management such as exhaustion, degradation, adjustment, and periodic inspection of various members including degradation of an image carrying member and replenishment and disposal of a developer during use of image forming apparatuses were performed by service men. However, as image forming apparatuses have come into wide use, the use status and usage of image forming apparatuses have become diversified, and a very large amount of image forming apparatuses are in use at present. Therefore, it is difficult for service men to perform maintenance and management of image forming apparatuses for users.
For this reason, an image forming apparatus having a process cartridge wherein an image carrying member is integrated with at least one of a developing means and a cleaning means has been developed. In an image forming apparatus having such a process cartridge, for example, a printer or a copier, when the process cartridge life expires due to exhaustion or degradation of an image carrying member in the process cartridge, a developer, or other parts or units, the operator, a general user with no technical knowledge, can easily maintain and manage the image forming apparatus by changing the process cartridge. In an image forming apparatus using such a process cartridge, which is indicated, for example, in Japanese Patent Publication Open to Public Inspection No. 279870/1986, the transfer material mounting direction coincides with the mounting and removing direction of a process cartridge mounted on the upper frame, and hence the operator can stand in front of the apparatus and open the upper frame so as to remove the process cartridge from the upper frame when changing the process cartridge. By doing this, expendable supplies can be easily handled or operated, and restrictions on the operation space can be minimized.
In an image forming apparatus using a process cartridge, when the process cartridge is to be replaced, that is, when the life (durable life, operation life) of the process cartridge expires due to exhaustion or degradation of parts or units in the process cartridge, the operator himself is required to replace it. Therefore, it is necessary to inform the operator of the replacement time. A method for informing an operator of the replacement time of a process cartridge is indicated, for example, in Japanese Patent Publication Open to Public Inspection Nos. 163276/1982 and 152263/1983. In these publications, an image forming apparatus wherein a mechanism for counting the number of revolutions of a photosensitive drum in a process cartridge is mounted and an indication of the process cartridge replacement time is indicated when the count reaches a predetermined number.
However, even when the process cartridge life is detected and indicated by the image forming apparatus indicated in Japanese Patent Publication Open to Public Inspection No. 163276/1982 or 152263/1983, the operator, who sees the indication, is required to open the outer case of the image forming apparatus, pull out the process cartridge from the interior, and replace it. Although the process cartridge life is detected and an indication for it is indicated, the process cartridge is required to be replaced by the operator. Such work is not only extremely troublesome and burdensome but also requires great strength for the operator when the process cartridge is heavy and large due to sophisticated performance and coloration of the image forming apparatus. Furthermore, when pulling out and removing the process cartridge, the operator is required to pass it from one hand to the other, and there is a possibility that the process cartridge is dropped accidentally, some developer scatters, and the operator gets hurt.